Great strides are presently being made to develop an automatic, fully implantable ventricular defibrillator. See, for example, U.S. Pat. Nos. Re. 27,652 and Re. 27,757, where the first concept of the automatic implantable ventricular defibrillator is described. Recent advances have also been made in enhancing the reliability of fibrillation detectors. In this latter regard, see copending U.S. patent applications Ser. Nos. 878,005 and 878,006, each filed on Feb. 15, 1978. Furthermore, as outlined in copending U.S. patent application Ser. No. 801,300, filed on May 27, 1977, steps have been taken to improve the reliability of the implanted defibrillator by the provision of circuitry which interrogates the implanted electronics to verify proper operation before a defibrillating shock is delivered.
Each of the foregoing advances is significant, and yet it must be recalled that the art of implantable defibrillators is in its infancy. Accordingly, there is a need for a patient communication channel in the implantable defibrillator, both for the peace of mind of the wearer (to know that his implanted device can be electively disenabled and explanted) and to avoid discomfort to the wearer (should the sensing circuit actually malfunction). In addition, there are other reasons for wanting wearer-recognizable stimuli to be delivered by the implanted defibrillator to the wearer.
It is toward the provision of an implantable defibrillator having a communication channel, that the present invention is directed.